Differential plane mirror systems

The Renishaw differential interferometer detector head allows measurement of the relative displacement between a fixed, reference mirror, and a moving measurement mirror.

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The RLD10-X3-DI detector head has been designed to mount to the external wall of a process chamber via a simple three-pin mount. There is no need to enter the chamber to align the detector head - integral beam steerers allow independent pitch and yaw adjustment of reference and measurement beam - and the design of the mounting system allows the detector head to be removed and repositioned with minimal effect on system alignment.

When using the differential interferometer, plane mirror targets are required on both the motion system and a fixed reference point e.g. column or tool.

The DI detector head is often specified as part of an RLE20 system; the high resolution RLU20 laser source being ideally suited to measurements in vacuum chambers and other strictly controlled environments.  They are also available in low power options for applications requiring a power dissipation lower than the specified < 2 W of the standard RLD.


Range 0 m - 1 m
Cyclic error<1 nm
Output signal formatDigital - RS422 quadrature
Analogue - 1 Vpp sine / cosine
Maximum velocity1 m/s
Laser typeHeNe (Helium / Neon), 632.8 nm, Class II
Laser lifetime>50,000 hours

Figures are based on using the RLD10-X3-DI head with an RLU20 laser unit

Features and benefits

  • Exceptional metrology
    ppb frequency stability and ultra low cyclic error, allowing output resolutions to 38.6 pm.
  • Differential configuration
    Measures the relative position of stage versus column, or workpiece versus tool, and eliminates common mode errors such as motion of the chamber sidewall associated with environmental fluctuations.
  • Rapid alignment
    Simple alignment from outside the process chamber using four integrated beam steerers (±1° pitch and yaw adjustment for both measurement and reference beams) to overcome chamber and mirror mounting tolerances.


Next steps

Contact us online if you require more information or you have a pricing query, or alternatively you may like to speak directly to your local Renishaw office.